1. Field of the Invention
The present invention relates to liquid jet apparatus provided with monitoring means which can observe the operating state of a liquid jet head such as an ink jet head or the like by a simple constitution.
2. Description of the Prior Art
Liquid jet recording apparatuses such as ink jet recording apparatuses or the like can be divided into three kinds of known apparatuses: electrostatic suction type; pressure jet type; and pressure pulse type. The former two types can easily observed as to their operating states since the control is performed by charging ink particles. However, they are not particularly suitable for use in a small-sized printer because the apparatus itself is large and is difficult to make relatively free maintenance.
On the other hand, the third pressure pulse type, particulary a drop on-demand type apparatus, is suitable for miniaturization and enables realization of a light-weight apparatus. This type of apparatus is constituted in a manner such that, for example, an electrical-mechanical transducing element such as a piezoelectric element or the like is provided to surround a nozzle part of a liquid jet head, and a voltage pulse is applied to this electrical-mechanical transducing element in order to allow a pressure wave to be generated, thereby causing a recording liquid such as an ink or the like to be discharged from the nozzle part.
In such a pressure pulse type apparatus, a problem is caused because it is difficult to provide monitoring means with high reliability and simple constitution for detecting the abnormal operation and performing processing to recover normal operation. For instance, a method has been proposed whereby two kinds of piezoelectric transducing elements for driving and detecting the operating state are provided for one head (refer to Japanese Patent Application Laid-open Publication No. 32572/1979). However, this method also has drawbacks, such as increased manufacturing cost since the constitution of the head complicated, and difficulties in desiging structure to obtain optimum liquid jet characteristis.